Commit | Line | Data |
---|---|---|
b257a10b MD |
1 | /* |
2 | * urcu.c | |
3 | * | |
4 | * Userspace RCU library | |
5 | * | |
6982d6d7 | 6 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
af02d47e | 7 | * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. |
b257a10b | 8 | * |
af02d47e MD |
9 | * This library is free software; you can redistribute it and/or |
10 | * modify it under the terms of the GNU Lesser General Public | |
11 | * License as published by the Free Software Foundation; either | |
12 | * version 2.1 of the License, or (at your option) any later version. | |
13 | * | |
14 | * This library is distributed in the hope that it will be useful, | |
15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | * Lesser General Public License for more details. | |
18 | * | |
19 | * You should have received a copy of the GNU Lesser General Public | |
20 | * License along with this library; if not, write to the Free Software | |
21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
54843abc PM |
22 | * |
23 | * IBM's contributions to this file may be relicensed under LGPLv2 or later. | |
b257a10b MD |
24 | */ |
25 | ||
fdf01eed | 26 | #define _BSD_SOURCE |
c1d2c60b | 27 | #define _GNU_SOURCE |
71c811bf | 28 | #define _LGPL_SOURCE |
82d50e1a | 29 | #define _DEFAULT_SOURCE |
27b012e2 MD |
30 | #include <stdio.h> |
31 | #include <pthread.h> | |
32 | #include <signal.h> | |
33 | #include <assert.h> | |
f69f195a | 34 | #include <stdlib.h> |
6d841bc2 | 35 | #include <stdint.h> |
f69f195a | 36 | #include <string.h> |
09a9f986 | 37 | #include <errno.h> |
e8043c1b | 38 | #include <poll.h> |
27b012e2 | 39 | |
999991c6 | 40 | #include "urcu/arch.h" |
d73fb81f | 41 | #include "urcu/wfcqueue.h" |
57760d44 | 42 | #include "urcu/map/urcu.h" |
af7c2dbe | 43 | #include "urcu/static/urcu.h" |
618b2595 | 44 | #include "urcu-pointer.h" |
bd252a04 | 45 | #include "urcu/tls-compat.h" |
71c811bf | 46 | |
4a6d7378 | 47 | #include "urcu-die.h" |
5bffdd5d | 48 | #include "urcu-wait.h" |
4a6d7378 | 49 | |
121a5d44 | 50 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
71c811bf | 51 | #undef _LGPL_SOURCE |
27b012e2 | 52 | #include "urcu.h" |
71c811bf | 53 | #define _LGPL_SOURCE |
27b012e2 | 54 | |
3a71751e PB |
55 | /* |
56 | * If a reader is really non-cooperative and refuses to commit its | |
57 | * rcu_active_readers count to memory (there is no barrier in the reader | |
9340c38d | 58 | * per-se), kick it after 10 loops waiting for it. |
3a71751e | 59 | */ |
9340c38d | 60 | #define KICK_READER_LOOPS 10 |
3a71751e PB |
61 | |
62 | /* | |
63 | * Active attempts to check for reader Q.S. before calling futex(). | |
64 | */ | |
65 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
66 | ||
999991c6 MD |
67 | /* If the headers do not support membarrier system call, fall back on RCU_MB */ |
68 | #ifdef __NR_membarrier | |
69 | # define membarrier(...) syscall(__NR_membarrier, __VA_ARGS__) | |
553b7eb9 MD |
70 | #else |
71 | # define membarrier(...) -ENOSYS | |
72 | #endif | |
73 | ||
64f469e6 MD |
74 | enum membarrier_cmd { |
75 | MEMBARRIER_CMD_QUERY = 0, | |
76 | MEMBARRIER_CMD_SHARED = (1 << 0), | |
77 | }; | |
553b7eb9 | 78 | |
fdf01eed | 79 | #ifdef RCU_MEMBARRIER |
834a45ba | 80 | static int init_done; |
1de4df4b | 81 | int rcu_has_sys_membarrier; |
834a45ba | 82 | |
02be5561 | 83 | void __attribute__((constructor)) rcu_init(void); |
fdf01eed MD |
84 | #endif |
85 | ||
86 | #ifdef RCU_MB | |
02be5561 | 87 | void rcu_init(void) |
e90a6e9c MD |
88 | { |
89 | } | |
90 | #endif | |
8a5fb4c9 | 91 | |
fdf01eed MD |
92 | #ifdef RCU_SIGNAL |
93 | static int init_done; | |
94 | ||
95 | void __attribute__((constructor)) rcu_init(void); | |
96 | void __attribute__((destructor)) rcu_exit(void); | |
97 | #endif | |
98 | ||
731ccb96 MD |
99 | /* |
100 | * rcu_gp_lock ensures mutual exclusion between threads calling | |
101 | * synchronize_rcu(). | |
102 | */ | |
6abb4bd5 | 103 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
731ccb96 MD |
104 | /* |
105 | * rcu_registry_lock ensures mutual exclusion between threads | |
106 | * registering and unregistering themselves to/from the registry, and | |
107 | * with threads reading that registry from synchronize_rcu(). However, | |
108 | * this lock is not held all the way through the completion of awaiting | |
109 | * for the grace period. It is sporadically released between iterations | |
110 | * on the registry. | |
111 | * rcu_registry_lock may nest inside rcu_gp_lock. | |
112 | */ | |
113 | static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER; | |
4de0cd31 | 114 | struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT }; |
27b012e2 | 115 | |
b0d5e790 MD |
116 | /* |
117 | * Written to only by each individual reader. Read by both the reader and the | |
118 | * writers. | |
119 | */ | |
bd252a04 | 120 | DEFINE_URCU_TLS(struct rcu_reader, rcu_reader); |
27b012e2 | 121 | |
16aa9ee8 | 122 | static CDS_LIST_HEAD(registry); |
27b012e2 | 123 | |
5bffdd5d MD |
124 | /* |
125 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
126 | * struct gp_waiters_thread objects. | |
127 | */ | |
128 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
129 | ||
6abb4bd5 | 130 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
131 | { |
132 | int ret; | |
09a9f986 PM |
133 | |
134 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 135 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
136 | if (ret) |
137 | urcu_die(ret); | |
09a9f986 | 138 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 139 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
140 | if (ret != EBUSY && ret != EINTR) |
141 | urcu_die(ret); | |
bd252a04 | 142 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 143 | cmm_smp_mb(); |
bd252a04 | 144 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 145 | cmm_smp_mb(); |
09a9f986 | 146 | } |
8999a9ee | 147 | (void) poll(NULL, 0, 10); |
09a9f986 PM |
148 | } |
149 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
150 | } |
151 | ||
6abb4bd5 | 152 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
153 | { |
154 | int ret; | |
155 | ||
6abb4bd5 | 156 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
157 | if (ret) |
158 | urcu_die(ret); | |
41718ff9 MD |
159 | } |
160 | ||
fdf01eed | 161 | #ifdef RCU_MEMBARRIER |
a4922ed9 | 162 | static void smp_mb_master(void) |
fdf01eed | 163 | { |
1de4df4b | 164 | if (caa_likely(rcu_has_sys_membarrier)) |
64f469e6 | 165 | (void) membarrier(MEMBARRIER_CMD_SHARED, 0); |
fdf01eed | 166 | else |
5481ddb3 | 167 | cmm_smp_mb(); |
fdf01eed MD |
168 | } |
169 | #endif | |
170 | ||
02be5561 | 171 | #ifdef RCU_MB |
a4922ed9 | 172 | static void smp_mb_master(void) |
40e140c9 | 173 | { |
5481ddb3 | 174 | cmm_smp_mb(); |
40e140c9 | 175 | } |
fdf01eed MD |
176 | #endif |
177 | ||
178 | #ifdef RCU_SIGNAL | |
78ff9419 | 179 | static void force_mb_all_readers(void) |
27b012e2 | 180 | { |
02be5561 | 181 | struct rcu_reader *index; |
e3b0cef0 | 182 | |
27b012e2 | 183 | /* |
5481ddb3 | 184 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
185 | * compiler barriers around rcu read lock as real memory barriers. |
186 | */ | |
16aa9ee8 | 187 | if (cds_list_empty(®istry)) |
27b012e2 | 188 | return; |
3a86deba | 189 | /* |
5481ddb3 | 190 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 191 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 192 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 193 | * cache flush is enforced. |
3a86deba | 194 | */ |
16aa9ee8 | 195 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 196 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 197 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 198 | } |
27b012e2 MD |
199 | /* |
200 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
201 | * |
202 | * Note that the pthread_kill() will never be executed on systems | |
203 | * that correctly deliver signals in a timely manner. However, it | |
204 | * is not uncommon for kernels to have bugs that can result in | |
205 | * lost or unduly delayed signals. | |
206 | * | |
207 | * If you are seeing the below pthread_kill() executing much at | |
208 | * all, we suggest testing the underlying kernel and filing the | |
209 | * relevant bug report. For Linux kernels, we recommend getting | |
210 | * the Linux Test Project (LTP). | |
27b012e2 | 211 | */ |
16aa9ee8 | 212 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 213 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 214 | pthread_kill(index->tid, SIGRCU); |
8999a9ee | 215 | (void) poll(NULL, 0, 1); |
09a9f986 PM |
216 | } |
217 | } | |
5481ddb3 | 218 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 219 | } |
9d7e3f89 | 220 | |
a4922ed9 | 221 | static void smp_mb_master(void) |
9d7e3f89 MD |
222 | { |
223 | force_mb_all_readers(); | |
224 | } | |
fdf01eed | 225 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 226 | |
bc6c15bb MD |
227 | /* |
228 | * synchronize_rcu() waiting. Single thread. | |
fca9fb96 MD |
229 | * Always called with rcu_registry lock held. Releases this lock and |
230 | * grabs it again. Holds the lock when it returns. | |
bc6c15bb | 231 | */ |
cfe78e25 | 232 | static void wait_gp(void) |
bc6c15bb | 233 | { |
fca9fb96 MD |
234 | /* |
235 | * Read reader_gp before read futex. smp_mb_master() needs to | |
236 | * be called with the rcu registry lock held in RCU_SIGNAL | |
237 | * flavor. | |
238 | */ | |
a4922ed9 | 239 | smp_mb_master(); |
fca9fb96 MD |
240 | /* Temporarily unlock the registry lock. */ |
241 | mutex_unlock(&rcu_registry_lock); | |
b0a841b4 | 242 | if (uatomic_read(&rcu_gp.futex) != -1) |
fca9fb96 | 243 | goto end; |
b0a841b4 MD |
244 | while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, |
245 | NULL, NULL, 0)) { | |
246 | switch (errno) { | |
247 | case EWOULDBLOCK: | |
248 | /* Value already changed. */ | |
fca9fb96 | 249 | goto end; |
b0a841b4 MD |
250 | case EINTR: |
251 | /* Retry if interrupted by signal. */ | |
252 | break; /* Get out of switch. */ | |
253 | default: | |
254 | /* Unexpected error. */ | |
255 | urcu_die(errno); | |
256 | } | |
257 | } | |
fca9fb96 MD |
258 | end: |
259 | /* | |
260 | * Re-lock the registry lock before the next loop. | |
261 | */ | |
262 | mutex_lock(&rcu_registry_lock); | |
bc6c15bb MD |
263 | } |
264 | ||
731ccb96 MD |
265 | /* |
266 | * Always called with rcu_registry lock held. Releases this lock between | |
267 | * iterations and grabs it again. Holds the lock when it returns. | |
268 | */ | |
fd189fa5 MD |
269 | static void wait_for_readers(struct cds_list_head *input_readers, |
270 | struct cds_list_head *cur_snap_readers, | |
271 | struct cds_list_head *qsreaders) | |
27b012e2 | 272 | { |
9340c38d | 273 | unsigned int wait_loops = 0; |
02be5561 | 274 | struct rcu_reader *index, *tmp; |
9340c38d MD |
275 | #ifdef HAS_INCOHERENT_CACHES |
276 | unsigned int wait_gp_loops = 0; | |
277 | #endif /* HAS_INCOHERENT_CACHES */ | |
27b012e2 | 278 | |
40e140c9 | 279 | /* |
c9488684 MD |
280 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
281 | * indicate quiescence (not nested), or observe the current | |
ed1b099e | 282 | * rcu_gp.ctr value. |
27b012e2 | 283 | */ |
cfe78e25 | 284 | for (;;) { |
5e81fed7 MD |
285 | if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) |
286 | wait_loops++; | |
9340c38d | 287 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
ed1b099e | 288 | uatomic_dec(&rcu_gp.futex); |
cfe78e25 | 289 | /* Write futex before read reader_gp */ |
a4922ed9 | 290 | smp_mb_master(); |
cfe78e25 MD |
291 | } |
292 | ||
fd189fa5 MD |
293 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
294 | switch (rcu_reader_state(&index->ctr)) { | |
295 | case RCU_READER_ACTIVE_CURRENT: | |
296 | if (cur_snap_readers) { | |
297 | cds_list_move(&index->node, | |
298 | cur_snap_readers); | |
299 | break; | |
300 | } | |
301 | /* Fall-through */ | |
302 | case RCU_READER_INACTIVE: | |
303 | cds_list_move(&index->node, qsreaders); | |
304 | break; | |
305 | case RCU_READER_ACTIVE_OLD: | |
306 | /* | |
307 | * Old snapshot. Leaving node in | |
308 | * input_readers will make us busy-loop | |
309 | * until the snapshot becomes current or | |
310 | * the reader becomes inactive. | |
311 | */ | |
312 | break; | |
313 | } | |
cfe78e25 MD |
314 | } |
315 | ||
e8043c1b | 316 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 317 | if (cds_list_empty(input_readers)) { |
9340c38d | 318 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 319 | /* Read reader_gp before write futex */ |
a4922ed9 | 320 | smp_mb_master(); |
ed1b099e | 321 | uatomic_set(&rcu_gp.futex, 0); |
bc6c15bb | 322 | } |
cfe78e25 MD |
323 | break; |
324 | } else { | |
fca9fb96 MD |
325 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
326 | /* wait_gp unlocks/locks registry lock. */ | |
cfe78e25 | 327 | wait_gp(); |
fca9fb96 MD |
328 | } else { |
329 | /* Temporarily unlock the registry lock. */ | |
330 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 331 | caa_cpu_relax(); |
fca9fb96 MD |
332 | /* |
333 | * Re-lock the registry lock before the | |
334 | * next loop. | |
335 | */ | |
336 | mutex_lock(&rcu_registry_lock); | |
337 | } | |
bc6c15bb | 338 | } |
e8043c1b | 339 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 340 | /* |
40e140c9 | 341 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
342 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
343 | * for too long. | |
27b012e2 | 344 | */ |
fd189fa5 | 345 | if (cds_list_empty(input_readers)) { |
9340c38d | 346 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 347 | /* Read reader_gp before write futex */ |
a4922ed9 | 348 | smp_mb_master(); |
ed1b099e | 349 | uatomic_set(&rcu_gp.futex, 0); |
cfe78e25 MD |
350 | } |
351 | break; | |
352 | } else { | |
9340c38d | 353 | if (wait_gp_loops == KICK_READER_LOOPS) { |
a4922ed9 | 354 | smp_mb_master(); |
9340c38d MD |
355 | wait_gp_loops = 0; |
356 | } | |
357 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { | |
fca9fb96 | 358 | /* wait_gp unlocks/locks registry lock. */ |
9340c38d MD |
359 | wait_gp(); |
360 | wait_gp_loops++; | |
361 | } else { | |
fca9fb96 MD |
362 | /* Temporarily unlock the registry lock. */ |
363 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 364 | caa_cpu_relax(); |
fca9fb96 MD |
365 | /* |
366 | * Re-lock the registry lock before the | |
367 | * next loop. | |
368 | */ | |
369 | mutex_lock(&rcu_registry_lock); | |
40e140c9 MD |
370 | } |
371 | } | |
e8043c1b | 372 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 373 | } |
27b012e2 MD |
374 | } |
375 | ||
9598a481 | 376 | void synchronize_rcu(void) |
2bc59bd7 | 377 | { |
fd189fa5 MD |
378 | CDS_LIST_HEAD(cur_snap_readers); |
379 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
380 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
381 | struct urcu_waiters waiters; | |
382 | ||
383 | /* | |
384 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
385 | * for a grace period. Proceed to perform the grace period only | |
386 | * if we are the first thread added into the queue. | |
387 | * The implicit memory barrier before urcu_wait_add() | |
388 | * orders prior memory accesses of threads put into the wait | |
389 | * queue before their insertion into the wait queue. | |
390 | */ | |
391 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
392 | /* Not first in queue: will be awakened by another thread. */ | |
393 | urcu_adaptative_busy_wait(&wait); | |
394 | /* Order following memory accesses after grace period. */ | |
395 | cmm_smp_mb(); | |
396 | return; | |
397 | } | |
398 | /* We won't need to wake ourself up */ | |
399 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 400 | |
6abb4bd5 | 401 | mutex_lock(&rcu_gp_lock); |
135530fd | 402 | |
5bffdd5d MD |
403 | /* |
404 | * Move all waiters into our local queue. | |
405 | */ | |
406 | urcu_move_waiters(&waiters, &gp_waiters); | |
407 | ||
731ccb96 MD |
408 | mutex_lock(&rcu_registry_lock); |
409 | ||
16aa9ee8 | 410 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
411 | goto out; |
412 | ||
731ccb96 MD |
413 | /* |
414 | * All threads should read qparity before accessing data structure | |
415 | * where new ptr points to. Must be done within rcu_registry_lock | |
416 | * because it iterates on reader threads. | |
417 | */ | |
9598a481 | 418 | /* Write new ptr before changing the qparity */ |
a4922ed9 | 419 | smp_mb_master(); |
9598a481 | 420 | |
9598a481 | 421 | /* |
c9488684 | 422 | * Wait for readers to observe original parity or be quiescent. |
731ccb96 MD |
423 | * wait_for_readers() can release and grab again rcu_registry_lock |
424 | * interally. | |
9598a481 | 425 | */ |
fd189fa5 | 426 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
427 | |
428 | /* | |
c9488684 | 429 | * Must finish waiting for quiescent state for original parity before |
ed1b099e | 430 | * committing next rcu_gp.ctr update to memory. Failure to do so could |
d40fde2c MD |
431 | * result in the writer waiting forever while new readers are always |
432 | * accessing data (no progress). Enforce compiler-order of load | |
ed1b099e | 433 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr. |
9598a481 | 434 | */ |
5481ddb3 | 435 | cmm_barrier(); |
9598a481 | 436 | |
5dba80f9 | 437 | /* |
5481ddb3 | 438 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
439 | * model easier to understand. It does not have a big performance impact |
440 | * anyway, given this is the write-side. | |
441 | */ | |
5481ddb3 | 442 | cmm_smp_mb(); |
67c2d80b | 443 | |
c9488684 | 444 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
ed1b099e | 445 | CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE); |
c9488684 MD |
446 | |
447 | /* | |
ed1b099e | 448 | * Must commit rcu_gp.ctr update to memory before waiting for quiescent |
c9488684 MD |
449 | * state. Failure to do so could result in the writer waiting forever |
450 | * while new readers are always accessing data (no progress). Enforce | |
ed1b099e | 451 | * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr. |
c9488684 MD |
452 | */ |
453 | cmm_barrier(); | |
454 | ||
455 | /* | |
456 | * | |
457 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
458 | * model easier to understand. It does not have a big performance impact | |
459 | * anyway, given this is the write-side. | |
460 | */ | |
461 | cmm_smp_mb(); | |
462 | ||
9598a481 | 463 | /* |
c9488684 | 464 | * Wait for readers to observe new parity or be quiescent. |
731ccb96 MD |
465 | * wait_for_readers() can release and grab again rcu_registry_lock |
466 | * interally. | |
9598a481 | 467 | */ |
fd189fa5 MD |
468 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
469 | ||
470 | /* | |
471 | * Put quiescent reader list back into registry. | |
472 | */ | |
473 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 474 | |
731ccb96 MD |
475 | /* |
476 | * Finish waiting for reader threads before letting the old ptr | |
477 | * being freed. Must be done within rcu_registry_lock because it | |
478 | * iterates on reader threads. | |
479 | */ | |
a4922ed9 | 480 | smp_mb_master(); |
2dfb8b5e | 481 | out: |
731ccb96 | 482 | mutex_unlock(&rcu_registry_lock); |
6abb4bd5 | 483 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
484 | |
485 | /* | |
486 | * Wakeup waiters only after we have completed the grace period | |
487 | * and have ensured the memory barriers at the end of the grace | |
488 | * period have been issued. | |
489 | */ | |
490 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 PM |
491 | } |
492 | ||
121a5d44 MD |
493 | /* |
494 | * library wrappers to be used by non-LGPL compatible source code. | |
495 | */ | |
496 | ||
497 | void rcu_read_lock(void) | |
498 | { | |
499 | _rcu_read_lock(); | |
500 | } | |
501 | ||
502 | void rcu_read_unlock(void) | |
503 | { | |
504 | _rcu_read_unlock(); | |
505 | } | |
506 | ||
882f3357 MD |
507 | int rcu_read_ongoing(void) |
508 | { | |
509 | return _rcu_read_ongoing(); | |
510 | } | |
511 | ||
121a5d44 | 512 | void rcu_register_thread(void) |
27b012e2 | 513 | { |
bd252a04 MD |
514 | URCU_TLS(rcu_reader).tid = pthread_self(); |
515 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
516 | assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); | |
02be5561 | 517 | |
731ccb96 | 518 | mutex_lock(&rcu_registry_lock); |
a77f7d82 MD |
519 | assert(!URCU_TLS(rcu_reader).registered); |
520 | URCU_TLS(rcu_reader).registered = 1; | |
02be5561 | 521 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 522 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
731ccb96 | 523 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
524 | } |
525 | ||
121a5d44 | 526 | void rcu_unregister_thread(void) |
27b012e2 | 527 | { |
731ccb96 | 528 | mutex_lock(&rcu_registry_lock); |
a77f7d82 MD |
529 | assert(URCU_TLS(rcu_reader).registered); |
530 | URCU_TLS(rcu_reader).registered = 0; | |
bd252a04 | 531 | cds_list_del(&URCU_TLS(rcu_reader).node); |
731ccb96 | 532 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
533 | } |
534 | ||
fdf01eed MD |
535 | #ifdef RCU_MEMBARRIER |
536 | void rcu_init(void) | |
537 | { | |
64f469e6 MD |
538 | int ret; |
539 | ||
fdf01eed MD |
540 | if (init_done) |
541 | return; | |
542 | init_done = 1; | |
64f469e6 MD |
543 | ret = membarrier(MEMBARRIER_CMD_QUERY, 0); |
544 | if (ret >= 0 && (ret & MEMBARRIER_CMD_SHARED)) { | |
1de4df4b | 545 | rcu_has_sys_membarrier = 1; |
64f469e6 | 546 | } |
fdf01eed MD |
547 | } |
548 | #endif | |
549 | ||
550 | #ifdef RCU_SIGNAL | |
02be5561 | 551 | static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) |
27b012e2 | 552 | { |
40e140c9 | 553 | /* |
5481ddb3 DG |
554 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
555 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
556 | * executed on. |
557 | */ | |
5481ddb3 | 558 | cmm_smp_mb(); |
bd252a04 | 559 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 560 | cmm_smp_mb(); |
27b012e2 MD |
561 | } |
562 | ||
8a5fb4c9 | 563 | /* |
02be5561 | 564 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
565 | * reader threads are calling rcu_register_thread(). |
566 | * Should only be called by a single thread at a given time. This is ensured by | |
731ccb96 MD |
567 | * holing the rcu_registry_lock from rcu_register_thread() or by running |
568 | * at library load time, which should not be executed by multiple | |
569 | * threads nor concurrently with rcu_register_thread() anyway. | |
8a5fb4c9 | 570 | */ |
02be5561 | 571 | void rcu_init(void) |
27b012e2 MD |
572 | { |
573 | struct sigaction act; | |
574 | int ret; | |
575 | ||
8a5fb4c9 MD |
576 | if (init_done) |
577 | return; | |
578 | init_done = 1; | |
579 | ||
02be5561 | 580 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 581 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 582 | sigemptyset(&act.sa_mask); |
02be5561 | 583 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
584 | if (ret) |
585 | urcu_die(errno); | |
27b012e2 MD |
586 | } |
587 | ||
02be5561 | 588 | void rcu_exit(void) |
27b012e2 | 589 | { |
71210954 MD |
590 | /* |
591 | * Don't unregister the SIGRCU signal handler anymore, because | |
592 | * call_rcu threads could still be using it shortly before the | |
593 | * application exits. | |
594 | * Assertion disabled because call_rcu threads are now rcu | |
595 | * readers, and left running at exit. | |
596 | * assert(cds_list_empty(®istry)); | |
597 | */ | |
27b012e2 | 598 | } |
5e77fc1f | 599 | |
fdf01eed | 600 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 601 | |
5e6b23a6 | 602 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 603 | |
5e77fc1f | 604 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 605 | #include "urcu-defer-impl.h" |